# What is Gravity waves: Definition and 95 Discussions

In fluid dynamics, gravity waves are waves generated in a fluid medium or at the interface between two media when the force of gravity or buoyancy tries to restore equilibrium. An example of such an interface is that between the atmosphere and the ocean, which gives rise to wind waves.
A gravity wave results when fluid is displaced from a position of equilibrium. The restoration of the fluid to equilibrium will produce a movement of the fluid back and forth, called a wave orbit. Gravity waves on an air–sea interface of the ocean are called surface gravity waves or surface waves, while gravity waves that are within the body of the water (such as between parts of different densities) are called internal waves. Wind-generated waves on the water surface are examples of gravity waves, as are tsunamis and ocean tides.
Wind-generated gravity waves on the free surface of the Earth's ponds, lakes, seas and oceans have a period of between 0.3 and 30 seconds (frequency between 3.3 Hz and 33 mHz). Shorter waves are also affected by surface tension and are called gravity–capillary waves and (if hardly influenced by gravity) capillary waves. Alternatively, so-called infragravity waves, which are due to subharmonic nonlinear wave interaction with the wind waves, have periods longer than the accompanying wind-generated waves.

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1. ### B Gravity waves and Planck's constant

Can the energy of a gravitational wave be related to Plancks constant?
2. ### I Gravity Wave Propagation: Negative Energy Pulse?

At 0:51 in this simulation video there seems to be a brief moment upon merging that these singularities produce what appears to be negative gravitational "Spike?" that seems to bulge spacetime in an opposite metric compared to normal spacetime flatness. Is this a quirk of the simulation or is...
3. ### B Gravitational Wave Background: The Mysteries of the Universe

I don't know if this is the ideal sub-forum for this but I'd like to know more about this very recent activity I first saw here >>>>>' It looks like this could be some actually testable, actual breakthrough advances in Physics and the evolution of our Universe. Any comments appreciated.
4. ### B Report shows gravity waves in clouds(?)

https://www.sciencealert.com/a-weather-satellite-has-captured-rarely-seen-gravity-waves-in-earth-s-atmosphere This shows satellite images of what are being called gravity waves in clouds. There is an explanation of what happens in the example, using a timelapse 'movie' Is this a nomen...
5. ### I Measuring Gravity Wave Time Distortion Accuracy

Has/Can gravity wave time distortions be measured to any degree of accuracy as does LISA measures space distortions? If not, why not?
6. ### I Gravity Waves or Gravity Delay: Exploring Both

Or both? The cycling between 'stretch' and 'squeeze' is caused by the orientation changing of the black holes with respect to us. Correct? This is understood as waves (or pulses) moving through space, Correct? So they take time to get to us. So, consider the orientation which yields us being...
7. ### B Black Hole Paradox: Exploring Gravity Waves

well since gravity waves are supposed to have mass, they are supposed to be effected by gravity itself, and :/ how are we supposed to detect gravitational waves emitted from a black hole when none can get out?
8. ### B How electromagnetic stellar gravity waves (GR) form the effects of sound waves at the LIGO observatory?

https://en.wikipedia.org/wiki/LIGO#/media/File:Simplified_diagram_of_an_Advanced_LIGO_detector.png The axis on the bottom of the graph depicts frequencies between 20-1000 Hz which are sound waves. Again, how can a sound wave (gravity waves) propagate in the near vacuum of stellar space...
9. ### I Determining Mass & Info of Merging Neutron Stars from LIGO Signal

How does one determine/calculate the masses, orbital period, and separation of two merging neutron stars from the characteristics of its gravity wave LIGO signal? And how does this information allow one to calculate the distance to the galaxy that housed the merger? And how can one calculate...
10. ### Exploring the Mystery of Hull Speed: The Online vs. Textbook Debate

There is a well known rule of thumb amongst sailors that a boat has a theoretical maximum speed called the hull speed, given by v_h \approx 1.34 \sqrt{L_{wl}}, where LWL is the waterline length of the hull. This so-called rule is pretty much complete rubbish; a boat can overcome this speed with...
11. ### B Gravity waves and density perturbations

I am totally confused. What is concerning the anisotropy the difference between re-entering gravity waves and re-entering density perturbations and more important for me what is then happening in the photon-baryon plasma between end of inflation and these re-enterings.
12. ### Picture of "Gravity waves" and Sprites on weather.com

This has to be a mistake right or just wacko. Not the sprites (which are awesome) but the reference to "gravity waves". I love spaceweather.site but those sure aren't gravity waves? http://spaceweathergallery.com/indiv_upload.php?upload_id=129854&PHPSESSID=pokk9dgvl9o46qaq17rq1jbms6
13. ### B FTL Gravity Waves: Is Faster-Than-Light Travel Possible?

On the one hand, gravity waves travel at c, but on the other hand, spatial expansion has no speed limit; ie, it can happen at FTL speeds. At first one might think, "So what? Gravity waves are gravity waves and spatial expansion is spatial expansion." But what is a gravity wave other than the...
14. ### I Gravity Waves: Measure Spacetime Stretch with a Ruler

Hi all, On the website of gravity waves by PhD comics: At minute 1 and 5 seconds to minute 1 minute 20 secs. "Now if the spacetime between you and me stretched or compressed, we wouldn't notice it if we had made marks on our metaphorical sheet...because these marks would also get...
15. ### B How do I calculate electron acceleration by gravitational waves

If the amplitude of gravitational waves, frequency of gravitational waves and the vector potential of magnetic field in surrounding of such waves are known then what would be the easiest way to calculate resultant acceleration of electrons? My above question is based on the various researches...
16. ### B Gravitational Waves: What Happens In Between?

Hi when i found out about the presence of gravity waves, i first thought 'what happens if they were to be reversed' and then i thought 'what happens to space time in between these waves?' thanks
17. ### What happens if you sail through gravity waves?

Hi I am currently writing a sci fi book for children, and I wonder what happens with a spacecraft if it sails through powerful gravity waves? Does it have any consequences for the ship/crew at all? How abundant are gravity waves in space if you are sailing between stars or galaxies? Thank you!
18. ### Stargazing New Radio Telescope is World's Largest

World's largest radiotelescope just completed. http://news.xinhuanet.com/english/2016-07/03/c_135485643.htm
19. ### B LIGO detects second gravity waves

http://news.mit.edu/2016/second-time-ligo-detects-gravitational-waves-0615 This seems to be the year of black holes, between LIGO, and new theories of black holes being 2D objects instead of 3D masses. Anyway, I thought this was very interesting news and wanted to share :)
20. ### I Gravitational Waves Vs. Aether Wind

The Michelson-Morley Experiment (as depicted in the scishow YouTube video "The Greatest Failed Experiment Ever") which was used to test for the effects of 'Aether Wind' appears to be almost, if not completely, the same setup as the one used in a gravitational-wave observatory. Why is the success...
21. ### I Does non-gravitational acceleration produce waves?

In view of the observational equivalence of gravity and acceleration, does acceleration produce ripples in spacetime, similar to gravity waves?
22. ### I Gravity Waves & Gravitomotive Force: Is Rotation Possible?

For a binary emitting gravity waves: are there any directions of space into which gravity waves are not emitted for reasons of symmetry? Also: a steadily rotating electric charge current causes a magnetostatic field A steadily rotating mass must cause a gravitomagnetostatic field. Electrostatic...
23. ### I Could pulsar timing arrays see primordial gravity waves?

Im wondering if pulsar arrays could see primordial gravity waves? I have understood the only way to seem them would be to a) via indirect imprint on CMB polarisation b) direct viewing via some gigantic space based interferometer like Big Bang Observer However I was looking at this image...
24. ### B Do Gravity Waves and Sound Waves Share Frequencies?

I read that they found gravity waves that have the frequency of 35 to 250 hz but are not these frequencies that of sound waves? I thought sound does not propagate in vacuum or is there a new kind of gravity vacuum that contains a gravity ether or dark matter?
25. ### I How Do Orbiting Black Holes Generate Gravitational Waves?

I am probably missing something, but it seems to me that the only way gravitational waves could be generated would be if the center of gravity of a massive body or system began oscillating somehow. The detection of such waves was recently reported and were supposedly generated by a pair of black...
26. ### Exploring Black Holes: Uncovering Inner Structures with Gravity Waves

I'm a structural engineer in Mississippi and I love all aspects of cosmology. I want to learn all I can about gravity wave technology. I was not expecting the level of detail that a single event is revealing. It's very interesting that they expect to see gravity waves from objects other than...
27. ### B Gravity waves And entanglement quesro

So this is going to sound ridiculous, but I want to push my curiosity to the limit. Gravitational waves propogate at the speed of light, like most things in the universe. My first question is : is this propogation slowed down by anything? The Higgs field perhaps? 2nd question ; I assume that...
28. ### Recording gravity waves over the noise floor

I'm curious as to how the gravity waves were recorded given how small the amplitude of the wave was/is. Was it not below the thermal noise floor? Were noise removal techniques used, etc? Also, what kind of sampling rate/bit depth was used? Thanks
29. ### Pull Mass from 2 Black Holes: Uncovering the Mystery of Gravity Waves

OK, in solar mass terms, 29+36=62 with 3 left over. Or make that 3 left out. This is a little-advertised mechanism for pulling mass from a black hole. And, since the output is gravity waves, it doesn't seem to be directly related to Hawking Radiation. Somehow intense gravity can scoop out...
30. ### Gravity Waves: Energy Transfer from Observation

I'd be interested in hearing some thoughts on this. Does the fact that a set of gravity waves were observed imply that some energy, presumably a very small amount, was transferred from the gravity wave to observing instruments? If so, where in the apparatus and how did this transfer occur?
31. ### Speed of Gravity Waves: An Unmeasured Assumption?

Many popular accounts claim that gravity waves move at the speed of light. Now, I know 2 things: Special relativity says their speed cannot be greater than the speed of light in a vacuum. Gravity is a different fundamental force than the electromagnetic force. The same goes for their fields...
32. ### Force based explanation of gravity waves still possible?

It's quite chilling that gravitational wave has been detected.. can force based explanation of gravity waves still be possible? How? or does it prove 100% that GR is true or gravity is really spacetime curvature?
33. ### Gravity Waves and Superposition?

So I heard the news today about gravity waves being confirmed. I really like learning about all the different types of waves and would like to expand my knowledge on gravitational waves. So, do gravitational waves abide by the superposition principle/property? Does anyone suggest a website or...
34. ### Dispersion of gravitational waves

The LIGO paper https://dcc.ligo.org/LIGO-P150914/public puts limits on the dispersion of gravitational waves, which can be interpreted as an upper limit of 10^-22 eV on the mass of the graviton. We all know that low-amplitude gravitational waves are supposed to propagate at c according to the...
35. ### What do the gravity waves seen by LIGO imply for QG?

LIGO will apparently announce on February 11, the detection at five plus sigma of gravity waves (3 solar masses of energy worth in about 100 seconds) emitted as two medium sized black holes of about 65 solar masses combined spiral into each other and merge into a single Kerr (i.e. spinning)...
36. ### Gravity wave cancellation cause space expansion?

Is it possible that the increased acceleration of the universe could be caused by the cancellation of gravity waves? If not, what would be the impact on space-time when gravity waves do cancel out?
37. ### Gravity waves and gravitational radiation

My understanding of electromagnetic radiation is this: When a charged particle accelerates, there is a change in its associated electric field at all points in space, though not instantaneously. The "electric field wave" is basically the propagation of the disturbance that occurs when the...
38. ### Are Gravitational Waves Lossy?

Not much more to my question than the title - I imagine that if they do exist they are probably lossy, else with all the potential wave generators that have been in existence generating waves for billions of years there would be lots of waves bouncing all over the place and they would be readily...
39. ### Gravity Waves & Gravitons: Exploring the Distortion of Space-Time

If a mass bends space-time somehow and then I nudge it, the bend changes. This distortion of space-time bend is supposedly expanding at the speed of light and could be called a "gravity wave" that carries energy. Why is this wave not the distortion that creates a "graviton" like EM and photons?
40. ### B Extreme Gravity Waves: A Phenomenon That Can Alter Time on Earth

-- Hi. When a gravity wave pass Earth then the time goes a little faster and/or slower. Can there be a phenomenon in the universe that create a gravity wave that is so curved, that when it pass earth, the time stop or go infinitely fast? Regards Magi --
41. ### Gravitational Waves and the Expansion of the Universe: Redshift or Not?

would gravitational waves redshift with the expansion of the universe ?
42. ### Why does the h tensor represent gravity waves?

What makes it more "gravity-wavy" than the fi or psi scalar of the vector perturbations? (Im talking about metric perturbations) Thanks!
43. ### Gravity Waves: Frequency & Understanding Needed

I got one solution for an simple ode that involving gravity wave frequency . Before going further I have to understand more about gravity wave . So I need your help guys ...
44. ### Detecting Gravity Waves: An Exploration of Using Them for Communication

Just watched Intersteller and my mind started running wild with all sort of fun thoughts. So I'm not sure how serious of a questions this is, but I got to thinking if it's possible to use gravity waves as a form of communication. And in turn, started wondering how said waves could be detected...
45. ### Was the announcement that BICEP2 has detected Inflation Gravity Waves premature?

Constraint on the primordial gravitational waves from the joint analysis of BICEP2 and Planck HFI 353 GHz dust polarization data It seems that the contamination of the BICEP2 signal by B Mode polarised light from galactic dust lanes might explain all the polarisation detected. I was at a...
46. ### Propagation of gravitational waves

Stumbled upon this problem lately. Maybe someone could help me clarify some subtleties I do not see? 1. Consider the propagation speed ##c## of periodic surface of gravity waves with wavelength ##\lambda## and amplitude ##a## in water of depth ##H##. Let ##\rho_{a}## and ##\rho_{w}## be the...
47. ### Why does inflation generate gravity waves?

I've been trying to understand the whole BICEP story. Here's what I think I understand so far: Inflation produces primordial gravitational waves. During recombination, photons decouple from matter and the CMB is formed. Propagating gravity waves stretch space in one direction and squeeze it in...
48. ### Can light produce weak gravity waves?

I have read online that light can produce a weak gravitational field (for example antiparallel beams should, in principle, attract weakly). This made me wonder if light can produce minute gravitational waves. Even if the waves were extremely weak (no disregarding of those high order terms in the...
49. ### Gravity Waves and Graceful Exit

Recently reading the Scientific American article The Black Hole at the Beginning of Time, which at first glance made me wonder if they were bowing to pressure to increase circulation, did however get me to thinking about Inflation and Graceful Exit, a rather major problem. I understand that...
50. ### Gravity Waves vs Elastic Sheet: Is the Analogy Productive?

The basic question was inspired by some other recent threads on the "fabric of space". If we imagine a 2-d spatial rubber sheet, how closely can we make its vibrational modes compare to gravity waves (in the limit of non-relativistic velocities). It's well known that gravity waves locally...